Zilean The Chronokeeper

Active: Zilean throws a ticking time bomb to a target location that detonates after 3 seconds, dealing magic damage in a 330-radius area. If the bomb lands within 100-units of a unit or a unit moves within range while the bomb is on the ground, it will attach to them and will detonate from their current position at the end of its lifetime.
If a bomb is placed on a unit already holding a bomb, the first will detonate immediately, also stunning all enemies in range for a brief duration.
Magic Damage: 75 / 115 / 165 / 230 / 300 (+ 90% AP)
Stun duration: 1.1 / 1.2 / 1.3 / 1.4 / 1.5
RANGE: 900
COST: 60 / 65 / 70 / 75 / 80 mana
COOLDOWN: 10 / 9.5 / 9 / 8.5 / 8

Active: Zilean places a protective time rune on an allied champion for 5 seconds.
If the target takes lethal damage during that time, they will be placed in stasis for 2 seconds, becoming untargetable and invulnerable but also unable to perform any action. When they come out of stasis , they are revived with a set amount of health.
Health Regained: 600 / 850 / 1100 (+ 200% AP)
RANGE: 900
COST: 125 / 150 / 175 mana
COOLDOWN: 120 / 90 / 60

Endgame items

Mid build

With this build you'll have hp and mana but you can change "rod of ages" with some other item if you are winning your lane. But you can also buy "rod of ages" when you dominate your lane to make sure you won't lose late game. This build is best when you have to go vs tanky enemies or assasins. If you are really losing your lane you can buy "doran ring" or "kages lucky pick" it will help you to get back on your feet. Zilean is middle game champion. Strong at start but if you fail with him it's hard to get back on feet unless enemy team has a lot of squshy champions.

Skillorder

Chanpion skills

With zilean it's better to max w as a second spell because it takes 10s of other spell coldowns. In late game zilean can get his ultimate in about 30s.(with max cd reduction). I max w as my second spell because i can make double boombs more often. Plus i can get my ultimate more faster

Summoner spells

Spells

Summoner spells

I take ignite and flash when i play wih zilean at mid, but ofcours you can also take clarity. Zilean is mana hungry, but if you can control the use of mana then there is no problems and you can take ignite.

Runes

Glymph

x9

Greater Glyph of Force

+0.17 ability power per level (+3.06 at champion level 18)

Mark

x9

Greater Mark of Insight

+0.95 magic penetration

Seal

x9

Greater Seal of Replenishment

+0.41 mana regen / 5 sec.

Quintessence

Runes

I like runes that give ap per level. In that way i may have less ap at the start but it will increase at the end. Even thought that 27ap isn't much i still like it. You can also buy other glyphs that give you ap instantly (your choise).